It is about the period of time when Alexandria was very volatile right before the collapse of the Roman Empire, and the events leading up to the burning of the Library at Alexandria and the murder of the thinker Hypatia.

It's a fairly realistic view of the struggles between Pagans, Christians, and Jews living in the time period. And the movie has received a lot of accolades from scholars in Europe apparently, it was ostricized by many Christian groups because of its portrayal of Christian violence and the group the Parabalani acting more like the Taliban.

The film has its historic errors, Hypatia did not develop the concept of the eliptical orbits of the planets, for one, but it did provide a decent backdrop. There are some other details, her death was considerably sanatized, the actions of pagans leading to the sacking of the libraries is not found in the sources, but was part of a wider crackdown on pagans at the time. I understand the director was pushing the theme that all religions can lead to violence if taken to that extreme; there are two particular sources, one written by a Christian, the other a Pagan, which provide conflicting accounts. It is a fact that the outlawing of Pagan religious practices was well underway during the period depicted in the film.